Telephone-transmitter



'e. K. THOMPSON.

TELEPHONE TRANSMITTER.

APPLICATION FILED SEPT. 21, I918.

Patented Sept. 28, 1920.

- INVENTOR.

Thompson BY M ATTORNEY GEORGE K. THOMPSON, OF MAPLEWOOD, NEVI JERSEY.

TELEGRAZH (JGMPANY. .4

TELEPHONE AND ASSIGNOR TO AMERICAN CORPORATION OF NEW YORK.

TELEPEIONE-TR-ANSMITTER.

Application filed September 21, 1918.

To all whom it may concern:

Be it known that I, Gnonen K. TrroMrsoN, residing Maplewood, in the county of Essex and State of New Jersey. have in vented certain Improvements in Telephone- Transmitters, of which specification.

his invention relates to improvements in telephone transmitters and consists in the production of an instrument of this character which has an increased efliciency in operation.

An object of the invention is the provision. of a transmitter possessing high normal resistance and capable of producing a wide variation in resistance in response to voice waves.

Another object consists in providing means whereby the electrodes with their associated elements, and the interposed granular material may be combined and inclosed in a compact and unitary structure. Other and further objects of the invention will more fully appear hereinafter.

In the drawing forming a portion of the specification, in which like numerals represent like parts .hroughout, Figure l is a side elevation of the improved transmitter shown in section; and Figs. 2 and 3 are views of the double front and back electrodes. respectively. used in connection with the improved transmitter, showing the insulatinp; means which is provided for the separation. of the two halves of said electrodes.

A transmitter mouthpiece 5 of ordinary form is secured to a front member 6 of a casino: having a back member 7. A diaphragm 8 rests against the inner surface of the front member 6. but is suitably insulated therefrom by a rubber gasket 8' provided about its periphery. A front plate 9. preferably of metal. is provided with a screw three ed stud 10 which passes through a hole in the center of the diaphragm 8 and engages a nut 11. The front member 6 is provided with a peripheral flange .12 to which the ends of a bridge 13 are detachably secured by screws 1 The principal elements of the transmitter are preferably assembled directly upon the bridge 13 so as to form a compact unitary structure which is readily detachable from other parts of the transmitter. The central portion of the bridge 13 preferably extends rearwardly, as illustrated, so as to form a recess or space Specification of Letters Patent.

the following is a Patented Sept. 28, 1920. Serial No. 255,133.

for the accommodation of the multiple-unit resistance chamber 15 and its associated elements. The chamber 15 is supported by its shank 16 which cooperates with a conducting block or brass bushing 17 insulated from and secured to the brid e member 13. The chamber comprises a metal cup provided with insulating lining 18 of any suitable material. such as mica or paper, and is provided its front face with an auxiliary diaphi gm of insulating material 19 which is kept snugly in place, though capable of vibratory movement. by any suitable means such as a can 20 peripherally secured to said chamber. Insulating members 21 and 21 are provided as shown in Figs. 2 and 3 which serve as an insulating means to separate the front electrodes 22. 22 and back electrodes 23. 23 respectively. The electrodes 22 and 22 are semi-circular in form and equipped with threaded projections which extend through apertures in the diaphragm 19. said projections being secured by means of. nuts to the front-plate 9 and being suitably insulated therefrom. The front plate 9 and diaphragm 19 are thus movable together and partake of the vibrations of the main diaphragm 8. The electrode members 23 and 23 are in like man ner secured to the rear of the cup member 15. but the member 23 is not insulated from said cup member and serves to provide a conductive path to the terminal by way of the flange 16 and metal bushing 17 as will presently appear.

A thin flexible partition or diaphragm 24 preferably of mica is centrally located within the chamber 15 between the electrode members 22. 22' and 23. 23. As the diaphragm functions to transmit freely the vibrations conveyed to it from its associate memcers. it is necessary that said diaphragm be sensitive and to this end it is preferably composed of thin mica in the order of M1000 of an inch or less. As the space on either side of the central diaphragm 24 and the electrodes is the same, an equal amount of comminuted material such as granular carbon is provided in each space so that the normal resistance of the granular material in both spaces is approximately the same.

Secured to the upper part of the rearwardlv extended. portion of the bridge 13 is a terminal 25 to which may be attached an outside conductor entering through an aperture in the back member 7 of the casing. Another terminal in the form of a block also adapted to engage with an outside conductor ina manner similar to terminal 25, is shown at 26, said terminal being provided with binding post screws 27 and 28. Both terminals are suitably insulated from the 7 bridge member 13.

The circuit connections are made from the terminal 26, bindingpost screw 28, conductor 29, lower front electrode 22, through the granular material in the front portion of the chamber 15, as shown by dotted lines, to the upper front electrode 22 and thence by conductor 30 to the upper back electrode 23 through the granular material in the back portion of the metal cup or chamber 7 metal bushing 17 to the terminal 25.

in one preferred form In the operation of the improved transmitter the movements of the main diaphragm 8 are communicated to the front electrodes mounted on the diaphragm 19 and upon the vibration of said electrodes the granular carbon in the front and rear compartments are compressed since the central diaphragm also acts in conjunction with the granular material and partalzes of the movement of the front electrodes and vibrates simultaneously therewith. As a consequence of this action a greater variation in resistance results from the Voice waves impressed upon the transmitter, while the peculiar structural arrangement above described secures a transmitter of high normal resistance thereby permitting of very efficient operations, especially in connection with long lines.

ll hile there is shown and described hereway of illustration, it is understood that it is not limited or confined to the precise details of construction heremdescribed and delineated, as modification and variation may be made within scope of the claims without departing from the spirit of the invention.

ing conductivelyattached The current in this of the invention by r Having now described my invention, what I claim and desire to secure .by Letters Patent is:

1. In a telephone transmitter, a variable resistance chamber comprising a casing, movable electrodes within the casing, a diaphragm cooperating with said movable electrodes, means for insulating the electrodes from each other and from the diaphragm, fixed electrodes secured to the casing, means for insulating the fixed electrodes from each other, one of said electrodes being insulated from the casing and the other electrode beto said casing, a second diaphragm between the movable electrodes and fixed electrodes, a compartment on either side of said second diaphragm, and a body of granular material provided in each of the compartments cooperating with the second diaphragm and movable and fixed electrodes.

2. In a telephone transmitter, a variable resistance chamber comprising a casing, a diaphragm, movable electrodes oi approximately semi-circular form attached to'said diaphragm, fixed electrodes of approximately semi-circular form attached to the casing, a central diaphragm flexibly attached to the casing between, the electrodes. compartments on either side of said central diaphragm, bodies of granular conducting material in each of said compartments cooperating with the central diaphragm and movable and fixed electrodes respectively, and means between the movable electrodes and fixed electrodes for individually insulating said electrodesfrom each other.

3. In a variableresistance chamber, a diaphragm,.movable electrodes fixed to the diaphragm, fixed electrodes, a flexible diaphragm between said movable and fixed electrodes, and independent bodies of granular conducting material between the movableelectrodes and fixedelectrodes and the flexible diaphragm respectively, and circuit connections 7 whereby the current flows through the two bodies ofgranular material in series and in a direction parallel to the flexiblediaphragm. V r

Intestimony' whereof, I have signed my name to this specification this 19th day of beptember, 1918. V

enoaen. K. THOMPSON. 

